It
can also result in what I like to call clustering schizophrenia, where both nodes begin failing
almost repeatedly, neither knowing which role it should be playing. This is a rare
situation, but it??™s a joy to watch and a nightmare to resolve.
In any active/active/active/ . . . configuration, the sum of the maximum memory on
all nodes should not exceed the maximum memory for any single node. And all of those
individual servers should be exactly the same, right?
CHAPTER 7 n CLUSTERING 190
SQL Clustering and AWE Memory
One great new feature of SQL Server 2005 is how clustering uses memory when Address
Windowing Extensions (AWE) is enabled. As I mentioned in the previous section, if
memory resources are misconfigured in a way that prevents both instances from running
on a single box, clustering will tend to, well, freak out.
When AWE memory is enabled (usually only done when more than 4GB of memory
is installed), SQL Server interacts with the operating system to dynamically reconfigure
the memory of the running instances so that they run together. There might be an
extreme performance hit, but at least the failover will work.
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